We have developed a human mammary cell culture system to use for studies of cellular differentiation and carcinogenesis. We will be using this system to investigate (1) properties that may differentiate between normal and malignant mammary epithelial cells (tumor specific antigens, karyology), (2) factors that stimulate growth of the human mammary epithelial cells, (3) expression of mammary specific properties (synthesis of medium chain fatty acids, presence of thioesterase II, pattern of glucose metabolism) in response to different media, (4) the effect of chemical carcinogens (e.g. benzo(a)pyrene) on expression of tumor specific properties.